Hardware based encryption is a topic within the field of device security and encryption. Physically unclonable functions (PUFs) can produce consistent outputs that are difficult to predict. PUFs can provide an attractive hardware encryption solution when implemented on a physical entity that is embodied in a physical structure (e.g., PUF circuit). A PUF device can be used to produce an unclonable cryptographic key that is resistant to physical attacks. In response to an input challenge, the PUF can generate a response that depends on the input challenge and the unique device-specific physical properties of the PUF device.
PUFs can be a combination of one or more integrated circuits or transistors manufactured with semiconductive material, and can generate a random, unique, and stable output (e.g., a random bit of 0 or 1) based on the underlying physical characteristic of the semiconductive material or integrated circuit. A PUF device can be difficult to duplicate, even given the exact manufacturing process and random process variations in the manufacture of each PUF device.
However, certain PUF devices produce noisy outputs and therefore fail to achieve the stability requirements for a function. For example, certain PUFs are subject to noise induced by temperature and supply voltage variations, and return slightly different responses when queried with the same challenge multiple times. Accordingly, there is a need for PUF devices that are resistant to temperature and supply voltage variations.